Studies of duration in low back pain have largely followed patients identified in the subacute phase (6 weeks to 6 months after onset) or chronic patients. Some inferences have been drawn about predictors of chronicity from etiologic studies on healthy subjects to learn if they subsequently had chronic episodes. In the proposed project, we will examine whether a group of patients at high risk of chronicity or recurrence can be identified during the acute phase of back pain (within one month of onset) based on information ascertained in routine clinical practice, thus filling the gap in current knowledge of this question. The identification of such a group can lead to studies of the effectiveness of acute phase interventions in high-risk patients in reducing the overall morbidity and costs of low back pain treatment. The proposed project is a prospective population-based study of predictors of outcome in low back pain, with an inception cohort of back pain patients from a population of 50,000 employed individuals. The study will be conducted in an environment where both Union and Management jointly support low back pain research. Data characterizing clinical signs and symptoms upon examination, demographics, attitudes towards work, expectations of recovery, working conditions, functional status and pain intensity will be gathered when an employee first presents at the clinic. The participating medical evaluation facilities see approximately 800 low back pain patients each year. Follow-up interviews will be conducted 3 months and 6 months after the initial visit. We will examine the relative importance of episode severity, back pain history, sociodemographic, attitudinal and work- related factors in predicting episode duration, recurrence of low back pain, and residual functional limitation after one year of follow-up. We plan to develop an algorithm for identifying patients at risk of chronicity and recurrence. Patterns and predictors of health care utilization and charges for back pain diagnosis and treatment will be examined in the same cohort.